The present invention relates to rotary sprinklers, and particularly to a rotary sprinkler of a construction which enables its rotational speed to be conveniently controlled. The invention also relates to a method of distributing water around a rotary sprinkler.
Various techniques have been developed for controlling the rotational speed of a rotary sprinkler. One common technique is to use a speed-reduction gearing, but such constructions are relatively expensive to produce and also to maintain. Another technique is to use a friction-type retarding device or a viscous-liquid type retarding device, but these techniques waste a significant part of the energy in the pressurized water supply, dissipating this energy as heat. The foregoing types of rotary sprinklers are also sensitive to pressure variations in the supply line.